The present invention relates to subcutaneous delivery of medication via a drug delivery system and, in particular is concerned with blocking the flow of medication when an infusion set becomes disconnected from the body of the patient. The self-occluding infusion set may be used together with a delivery system sensitive to flow blockage in order to trigger an alarm under circumstances in which the medication would otherwise be delivered outside the patient's body.
It is known that automated drug delivery systems provide a reliable means for administering medication at a prescribed dosage over an extended period. These systems typically include a medication pump connected to an infusion set attachable directly to the patient's body, and a cannula for delivering the medication subcutaneously. Under normal circumstances the medication flows through the system into the patient's body in a controlled and consistent manner. However, such automation alone is not failsafe; fluid flow blockage (occlusion) occasionally occurs, preventing delivery of the medication to the patient. To address such problems, most drug delivery systems include an alarm system designed to alert the user when a blockage occurs so that he may take appropriate measures. Occlusion of the flow path results in a sudden increase in backpressure in the drug outlet flow path, thereby rendering the malfunction relatively easy to detect.
A more problematic situation is caused if the infusion set becomes disconnected from the patient's body. In this case, there is typically no detectable change in operating pressure along the flow path, such that the system may continue to deliver medication outside the body without generating any indication of malfunction. This may leave the patient oblivious to the fact that he is not receiving the required medication, resulting in a potentially life threatening situation even during waking hours and particularly during sleeping hours.
There is therefore a need for an infusion set that facilitates the detection of non-delivery of medication to the patient in situations the infusion set has become disconnected from the body.